1. Field of the Invention
This invention relates to an immersion supporting plate cleaning method for cleaning the immersion supporting plate provided around a substrate to be processed in immersion exposure, and a pattern forming method for forming a pattern by immersion exposure using an immersion supporting plate cleaned by the method.
2. Description of the Related Art
Of the known immersion exposure techniques, one of them involves forming an immersion area locally on a substrate to be processed, and then performing exposure while moving the immersion area over the substrate to be processed. To expose the peripheral part of the substrate to be processed, an immersion supporting plate is provided around the substrate to be processed so as to be as high as the substrate in order to maintain the immersion area in exposing the periphery of the substrate to be processed.
Because of various factors, foreign substances, such as particles, can adhere to the immersion supporting plate. Cleaning to remove the foreign substances was done on almost the entire surface of the immersion supporting plate. However, depending on the cleaning method, the following problem arose: the problem of failing to remove the particles properly, such as the problem of spreading foreign substances or of failing to remove foreign substances completely. Moreover, there was another problem: it took much time to clean all of the immersion supporting plate (Jpn. Pat. Appln. KOKAI Publication No. 2005-79222, Jpn. Pat. Appln. KOKAI Publication No. 2006-49757, and Jpn. Pat. Appln. KOKAI Publication No. 2006-134999).
The immersion area is wider than the exposure area. In the area through which and with which the immersion area passes and makes contact in an exposure operation, since the area is cleaned by the immersion area, particles are less liable to produce. However, in the periphery of the immersion area which the immersion area doesn't contact at all, particles are liable to produce.
At the immersion boundary, the boundary between the immersion area contact part and the immersion area noncontact part, varies, depending on an exposure area (in other words shot size that is depended on the exposure mask pattern) or an exposure map. Therefore, when the substrate to be processed is exposed on the basis of a different exposure area or a different exposure map, the individual boundary areas shift. When the already exposed immersion boundary (a first immersion boundary) is located inward of an immersion boundary (a second immersion boundary) to be exposed next, the particles remaining in the first immersion boundary will be involved in the next exposure. For this reason, the following problems arose: the problem of the exposure characteristic being affected and the problem of permitting particles to increase on the substrate to be processed.
As described above, in the conventional immersion exposure apparatus or immersion exposure method, particles produced at the immersion supporting plates provided around the substrate to be processed, which was the factor that causes exposure failure and a decrease in the exposure accuracy.